The present invention relates to a method for operating a magnetic recording and reproducing apparatus of the rotary head type, such as an R-DAT (rotary head type digital audio tape recorder). More particularly, the invention relates to a method for operating a rotary head type digital signal reproducing apparatus which is capable of reproducing programs recorded on a magnetic tape in different recording modes.
In an R-DAT, a magnetic tape is run at a predetermined speed around the periphery of a drum, at an angle of 90.degree. relative to the rotational axis of the drum, while the drum is being rotated at a speed, for example, of 2,000 rpm. The program is recorded on the tape in the form of a plurality of parallel slanted tracks, adjacent ones of which are recorded and reproduced by two respective recording and reproducing heads mounted on a rotating drum. Each track includes, arranged in the direction in which the head rotates, a sub-code area, an ATF region, and a PCM region.
Three different tape running speeds are employed in present-day R-DATs, namely, an ordinary X1 speed of 8.150 mm/sec (normal speed mode), a X1.5 speed of 12.225 (wide track mode), and a X0.5 speed of 4.075 mm/sec (half speed mode). The wide track mode is employed to allow a contact printer to run at high speed, and the half speed mode is employed to provide the recorder with an extended playing time mode.
Moreover, different sampling frequencies are employed for the various modes, for example, 48, 44.1 and 32 kHz. Also, different numbers of quantization bits and different quantization techniques are sometimes used, namely, 16 bits in the case of linear quantization and 12 bits in the case of nonlinear quantization Even in the case of 12-bit quantization, different recording modes are often employed, for example, a long playing mode in which the tape speed is reduced by a factor of one-half and a four-channel mode in which the standard tape speed of 8.150 mm/sec is used and the number of channels is doubled.
Of course, not every R-DAT is capable of operating with all combinations of the parameters mentioned above. When it is attempted to play a tape having a selection previously recorded on another apparatus in a mode in which the present playing apparatus is not capable of operating, the result is either noise or a muted output. Thus, the user is forced to manually search the tape for a selection recorded in a mode in which his or her recorder is capable of operating.